Abstracted/indexed

This paper describes GeoChronR, an R package that streamlines the process of quantifying age uncertainties, propagating uncertainties through several common analyses, and visualizing the results. In addition to describing the structure and underlying theory of the package, we present five real-world use cases that illustrate common workflows in GeoChronR. GeoChronR is built on the Linked PaleoData framework, is open and extensible, and we welcome feedback and contributions from the community.

In this study, we built a statistical model to determine the initial δ²³⁴U in submerged calcite crusts that coat the walls of Devils Hole 2 (DH2) cave (Nevada, USA) and, using ²³⁴U-²³⁸U dating method, extended the chronology of the calcite depostion beyond the previous well-established ²³⁰Th ages, and determined the oldest calcite deposited in this cave, a time marker for cave genesis. The novel method presented here may be used in future speleothem studies in similar hydrogeological settings.

Orakei Basin, a former maar lake in Auckland, New Zealand provides an outstanding sediment record over the last ca. 130,000 years but an age model is required to allow the reconstruction of climate change and volcanic eruptions contained in the sequence. To construct a relationship between depth in the sediment core and age of deposition, we combined tephrochronology, radiocarbon dating, luminescence dating, and the relative intensity of the paleomagnetic field in a Bayesian age-depth model.

This contribution present a new reference material, ASH-15 flowstone with an age of 2.965 ± 0.011 Ma (2σ), to be used for in-situ U-Pb dating of carbonate material. The new age analyses include the use of the EARTHTIME isotopic tracers and a large number of sub-samples (n = 36) with small aliquots (1–7 mg) each that are more representative of laser-ablation spot analysis. The new results could improve the propagated uncertainties on the final age with a minimal value of 0.4 %.

Unetched and etched apatites of five samples were dated by U–Pb with laser ablation inductively coupled plasma mass spectrometry. Our experiment demonstrates that the etching, needed for the apatite fission track dating, has no important effect on the obtaining of U–Pb ages; and therefore, the laser ablation-based technique can be used for apatite fission track and U–Pb double dating.

We characterize three natural carbonate samples with elevated uranium/lead (U/Pb) ratios to demonstrate techniques for characterizing carbonates for U/Pb dating. With the rapidly accelerating application of laser ablation analyses, there is a great need for well-characterized standards. The three samples we describe have good potential as standards. In addition to U/Pb data, we present strontium (Sr) isotope analyses to demonstrate that these could be dual standards for U/Pb and Sr isotopes.

This manuscript describes a new method of U-Pb calcite dating by laser ablation using a new detector array that allows for higher precision and lower limits of detection. This method thereby increases the likelihood of success in dating any given sample. I also explore how concentration of U and Pb, laser spot size and repetition rate, and mass spectrometer selection influence the final precision on the age, as to make recommendations for those interested in dating such samples.

Luminescence properties of samples from the northern foreland of the Swiss Alps are assessed. While signal loss is observed for the feldspar and polymineral, correction leads to feldspar ages that are consistent with those derived from quartz. In general, ages of the coarse-grained quartz and feldspar as well as the fine-grained polymineral fractions are in agreement. Ages indicate sedimentation of ca. 17 m during MIS 6 with a rapid transition from a lacustrine to a colluvial landscape.

Potassium-based geochronology, including the ⁴⁰Ar/³⁹Ar and K-Ar methods, provides critical constraints on the timing and duration of many events and processes in earth history. These methods assume that a key parameter, the fraction of potassium with a mass of 40, does not vary in some relevant materials. Some recent work has identified some variability in these materials. This work examines the effects of this variability on calculated K-Ar and ⁴⁰Ar/³⁹Ar ages.

The North American Varve Chronology is a sequence of 5659 annual sedimentary layers that were deposited in proglacial lakes adjacent to the retreating Laurentide Ice Sheet ca. 12,500 - 18,200 years ago. We attempt to synchronize this record with Greenland ice core and other climate records that cover the same time period by detecting variations in global fallout of atmospherically-produced beryllium-10 in NAVC sediments.

We compare two published U-Pb and ⁴⁰Ar/³⁹Ar geochronologic datasets used to produce different eruption rate models for the Deccan Traps LIP. We conclude that differences in eruption rates arise not from inaccuracy of dates, but instead from the way the data were presented. Applying the same statistical approach to each dataset, the resulting models agree well, but the higher precision U-Pb dataset generates a more nuanced eruption model that is untestable with the lower precision ⁴⁰Ar/³⁹Ar data.

Meteoric Beryllium-10 concentrations in soil profiles have great capacity to quantify earth surface processes, such as erosion rates and landform ages. However, determining these requires an accurate estimate of the delivery rate of this isotope to local sites. We present a new method to constrain the long-term delivery rate to a western US site and then compare it against existing delivery rate estimates, revealing considerable disagreement between methods, and suggest best practices.

⁴⁰K is an isotope of potassium that undergoes several different modes of radioactive decay. We use the decay of ⁴⁰K to determine the ages of geologic materials that contain potassium, but doing this requires us to know the rate at which ⁴⁰K decays by its different decay modes. Here, we investigate one decay mode of ⁴⁰K that has previously been overlooked. We demonstrate that this decay mode exists, estimate its rate, and evaluate its significance for geochronology.

A new methodology for the micron-scale uranium-lead dating of carbonate minerals is proposed. It is based on the extraction of ages directly from the pixels images (< 1 mm²) obtained by laser ablation coupled to a mass spectrometer. The ages are calculated with a robust linear regression through the pixel values, which is an efficient and simple approach to that can be easily applied to mineral dating.

Using a relatively new dating technique, in situ Rb-Sr geochronology, we constrain the ages of two generations of mineral assemblages from the Tropicana Zone, Western Australia. The first dated at ca. 2535 Ma is associated with exhumation of an Archean craton margin and gold mineralization. The second, dated at ca. 1210 Ma, has not been previously documented in the Tropicana Zone. It is probably associated with Stage II of the Albany-Fraser Orogeny and additional gold mineralization.

Cassiterite is the primary ore mineral of tin and is associated with lots of other elements we need for green technology. It is deposited from fluids that are released from magmas. Because it is extremely acid resistant there has been difficulty in dissolving the mineral for analysis, we use a novel method to dissolve and extract radiogenic isotopes of the uranium to lead decay scheme from Cassiterite and analyse its age thus improving the ability to work out the formation processes.